This is the role of a species in an ecosystem consisting of such things as what it eats, when it eats, and where it lives

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.